The present invention relates to mixing valves and more particularly to valve devices for setting limits on the characteristics of the fluid emanating from the mixing valve.
The single-handled mixing valve has been a fixture of plumbing for well over forty years. It established new standards in terms of consumer convenience since both the temperature and the flow rate of the mixture could be controlled by a single element. Such valves fall into two broad categories, the first a ball valve and the second a plate valve.
A ball valve comprises a stem connected to a spherical valve and moveable through a range of motions to allow appropriate registry of hot and cold inlet passages with a mixed flow output. This type of valve is renowned for its reliability since the stem is rigidly connected to the sphere and moveable parts are kept to a minimum. While a number of proposals have been made to limit maximum temperatures, these proposals either require use of tools and/or disassembly of the entire unit to change maximum temperature settings.
The second form of a plate valve comprises a plate moveable in two directions to provide variable registry with hot and cold inlet passages and a common output. The plate is moved through this range of displacement by a stem and a corresponding actuating mechanism.
In this era of consumer awareness, several control features are deemed to be necessary. One feature is to set an external limit on temperature so as to prevent inadvertent manipulation to a temperature output higher than is appropriate for the user. The second feature is that in some areas where the water supply is particularly scarce and expensive, it is important to place a limit on the maximum flow from such a valve. Again, it is desirable to achieve an adjustable maximum for these values without special tools or disassembly.